most of gilts
By Sue Rider
UNDER-FEEDING protein to gilts in the rearing stage hits reproductive performance.
The message of Julian Wiseman of the University of Nottingham counters conventional thinking on gilt rearing.
"Modern genotypes have a large mature size and a potentially high total lean mass. They are also being bred earlier, so are likely to be bred below their lean tissue potential.
"But the focus still tends to be on fat deposition to support pregnancy and lactation. Advice when rearing gilts has been to concentrate on feeding for adequate fat content and not to worry about feeding for a high lean tissue content," said Dr Wiseman. "Some advice has even advocated feeding low protein diets."
At the same time, MLC data shows that up to 50% of first parity sows in the UK are culled – with half due to failure to rebreed after weaning. Dr Wiseman was keen to find out whether there was a link between poor reproductive performance and failure to maximise growth of lean tissue.
His work at Nottingham, alongside colleague Jane Cameron, has studied the effects of feeding for lean tissue growth rates – with one group of gilts fed for maximum lean tissue growth and the other group for 80% of that.
Results showed that rearing gilts to achieve their maximum potential lean tissue growth increased ovulation rates at third oestrus. "Two and a half more eggs were shed," said Dr Wiseman.
"This underlines the importance of lean tissue reserves and demands a major rethink about the way we feed pigs. Make sure you rear the gilt to achieve high levels of protein growth. When the sow fails to reach her potential she wont have the metabolic stability for effective lifetime reproductive performance."
Dr Wiseman suggested contacting breeding companies to find out lean tissue growth potential of your gilts. "Then make sure you feed them accordingly."
SACs Anna Sinclair also warned of the dangers of underfeeding protein to maiden gilts. "Dont restrict protein intakes – accept that modern pigs are going to grow bigger," Dr Sinclair told the meeting. "Restricting protein can reduce ovulation rates and reduce litter size by one piglet."
• Feed adequate protein.
• Promote lean tissue growth.
• Modern gilts grow bigger.